We have now been able to freeze all the virus crystals mentioned below. Thus, nearly all our data this year were of frozen crystals. This created vast new possibilities. In the past, we have had to use one new crystal every two to six exposures (depending on the crystals). Now we can collect a whole data set (often almost 500 exposures) with a single crystal. That makes possible a vast new array of experiments with mutants and ligands that were not readily possible previously. (a) Parvoviruses The following conditions were explored for feline and canine parvoviruses. (i) pH changes from 5.5 to 7.2. This alters the ability to hemagglutinate, in other words, alters the ability of the virus to bind to specific receptors in the Rhesus monkey erythrocytes. (ii) The effect of Ca2+ ions. These ions are associated with changes of conformation of the hemagglutinating loop on the viral surface. (iii) Soaking and co-crystallization with various sialic acids, which are the terminal carbohydrate residues used by the virus in binding host cells. We have also obtained some initial diffraction patterns of porcine parvovirus capsids assembled in a baculovirus expression system. (b) Picornaviruses We have collected complete data sets of some antiviral compounds bound to human rhinovirus 16 (HRV16). We have collected complete data sets of some drug-dependent HRV16 mutants. These viruses are unstable in the absence of drug. We collected some MAD data on ICAM-1, the receptor to the major group of rhinoviruses. We solved this structure and have fitted the structure into cryo-EM reconstructions of the complex of ICAM-1 with HRV16. This is the first atomic resolution study of a proteinaceous receptor interaction with a virus. We obtained some initial results on crystals of encephalomyocarditis virus. (c) Microviridae We have collected a partial, relatively low resolution data set of a3, an E. coli bacteriophage homologous to fX174. (d) Other Results We collected data on crystals of a mutant of the "whisker" protein of phage T4 (this was "warm" data). We obtained initial results of crystals of the prolate head of phage f2